Bonding Impairment as an Explanatory Link between Unplanned Pregnancy and Maternal Infant Abuse: Results of a Causal Mediation Analysis.

Introduction: Unplanned pregnancy is associated with maternal-infant abuse. We investigated the association between unplanned pregnancy and maternal abusive behaviors and whether this relationship is mediated by bonding impairment. Methods: We analyzed data from a sample of mothers with 3-4-month-old infants in Japan (n = 5,706). Multivariable logistic regression models were used to assess the associations among unplanned pregnancy, bonding impairment, and maternal-infant abuse. Causal mediation analysis was conducted to estimate the mediating effect of bonding impairment on the relationship between unplanned pregnancy and maternal-infant abuse. Results: Among mothers who engaged in infant abuse, 24.8% reported an unplanned pregnancy, compared to 17.7% among those who did not. Unplanned pregnancy was significantly associated with an increased risk of maternal-infant abuse in a multivariable analysis (adjusted odds ratio [OR] = 1.36; 95% confidence interval [CI], 1.02-1.80). After adjusting for bonding impairment as a mediator, the association was attenuated (OR = 1.28; 95% CI, 0.96-1.70). Causal mediation analysis revealed a natural direct effect of unplanned pregnancy on maternal-infant abuse (OR = 1.28; 95% CI, 0.96-1.70), as well as a natural indirect effect through bonding impairment as a mediator (OR = 1.06; 95% CI, 1.03-1.09). Bonding impairment accounted for 20.1% of the association between unplanned pregnancy and maternal-infant abuse. Conclusions: Bonding impairment partially mediates the relationship between unplanned pregnancy and maternal-infant abuse.